ScheduleDFS.h - Replace ArrayRef.h include with forward declaration. NFC.

We have no need to include the entire header.

Author: RKSimon

llvm/include/llvm/CodeGen/ScheduleDFS.h

@@ -13,7 +13,6 @@
 #ifndef LLVM_CODEGEN_SCHEDULEDFS_H
 #define LLVM_CODEGEN_SCHEDULEDFS_H
 
-#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/CodeGen/ScheduleDAG.h"
 #include <cassert>
@@ -22,6 +21,7 @@
 
 namespace llvm {
 
+template <typename T> class ArrayRef;
 class raw_ostream;
 
 /// Represent the ILP of the subDAG rooted at a DAG node.